Apparatus with Mixed Fuel Separator and Method of Separating a Mixed Fuel

ABSTRACT

A method of operating a vehicle system including an internal combustion engine is disclosed, the method comprises separating a second fuel from a first fuel, the second fuel having a greater concentration of at least one component than the first fuel; combusting at least the first fuel at least during a first engine load; and combusting at least the second fuel at least during a second engine load higher than the first engine load.

The present application is a continuation of U.S. patent applicationSer. No. 11/384,142, filed Mar. 17, 2006, and entitled “Apparatus withMixed Fuel Separator and Method of Separating a Mixed Fuel”, the entirecontents of which are incorporated herein by reference. The presentapplication is also a continuation of U.S. patent application Ser. No.11/384,111, filed Mar. 17, 2006, and entitled “Control for KnockSuppression Fluid Separator in a Motor Vehicle”, the entire contents ofwhich are incorporated herein by reference

BACKGROUND AND SUMMARY

Engines may use various forms of fuel delivery to provide a desiredamount of fuel for combustion in each cylinder. One type of fueldelivery uses a port injector for each cylinder to deliver fuel torespective cylinders. Still another type of fuel delivery uses a directinjector for each cylinder.

Further, engines have been proposed using more than one type of fuelinjection. For example, the papers titled “Calculations of KnockSuppression in Highly Turbocharged Gasoline/Ethanol Engines Using DirectEthanol Injection” and “Direct Injection Ethanol Boosted Gasoline EngineBiofuel Leveraging for Cost Effective Reduction of Oil Dependence andCO2 Emissions” by Heywood et al. are one example. Specifically, theHeywood et al. papers describe directly injecting ethanol to improvecharge cooling effects, while relying on port injected gasoline forproviding the majority of combusted fuel over a drive cycle. The ethanolprovides increased octane and increased charge cooling due to its higherheat of vaporization compared with gasoline, thereby reducing knocklimits on boosting and/or compression ratio. Further, water may be mixedwith ethanol and/or used as an alternative to ethanol. The aboveapproaches purport to improve engine fuel economy and increaseutilization of renewable fuels.

However, the inventors herein have recognized several issues with suchan approach. Specifically, requiring a user to always provide separatefuels (e.g., gasoline and ethanol) can be burdensome to the operator. Tosimplify use of an engine with more than one type of fuel injection, theinventors herein have recognized that such an approach may be moreeasily implemented by the use of a mixed fuel in conjunction with aseparator disposed between a fuel tank and internal combustion engine,and by the use of a method comprising inputting a mixed fuel containinga hydrocarbon component and an oxygenated component into the separator,separating the fuel in the separator into a first hydrocarbon-enrichedfuel fraction and a second oxygenated fuel-enriched fuel fraction, andcontrolling an amount of the first fuel fraction and an amount of thesecond fuel fraction provided to the engine based upon an engineoperating condition. This approach takes advantage of already availablegas/alcohol mixtures, and therefore may allow advantages of multipleinjection and/or multiple fuel strategies to be employed withoutinconveniencing a user.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic diagram of a generic engine system.

FIG. 2 shows a partial view of an exemplary embodiment of an engine.

FIG. 3 shows an exemplary embodiment of a fuel system with a fuelseparator.

FIG. 4 shows a flow diagram of an exemplary embodiment of a method ofoperating an engine.

FIG. 5 shows a block diagram of another exemplary embodiment of a fuelseparator with a fuel separator.

FIG. 6 shows a block diagram of another exemplary embodiment of a fuelsystem with a fuel separator.

FIG. 7 shows a sectional view of an exemplary embodiment of a fuelseparator.

FIG. 8 shows a sectional view of another exemplary embodiment of a fuelseparator.

FIG. 9 shows a sectional view of another exemplary embodiment of a fuelseparator.

FIG. 10 shows a sectional view of another exemplary embodiment of a fuelseparator.

FIG. 11 shows a schematic view of another exemplary embodiment of a fuelseparator.

FIG. 12 shows a block diagram of another exemplary embodiment of a fuelsystem with a fuel separator.

FIG. 13 shows a block diagram of another exemplary embodiment of a fuelsystem with a fuel separator.

FIG. 14 shows a block diagram of another exemplary embodiment of a fuelsystem with a fuel separator.

DETAILED DESCRIPTION

FIG. 1 shows an engine 10 receiving delivery of a plurality ofsubstances (1, 2, . . . , N) via arrow 8. The various substances mayinclude multiple different fuel blends, injection locations, or variousother alternatives. In one example, multiple different substances havingdifferent gasoline and/or alcohol and/or water, and/or other compoundconcentrations may be delivered to the engine, and may be delivered in amixed state, or separately delivered. Further, the relative amountsand/or ratios of the different substances may be variable controlled bya controller 6 in response to operating conditions, which may beprovided via sensor(s) 4.

In one example, the different substances may represent different fuelshaving different levels of alcohol, including one substance beinggasoline and the other being ethanol. In another example, engine 10 mayuse gasoline as a first substance and an alcohol containing fuel such asethanol, methanol, a mixture of gasoline and ethanol (e.g., E85 which isapproximately 85% ethanol and 15% gasoline), a mixture of gasoline andmethanol (e.g., M85 which is approximately 85% methanol and 15%gasoline), a mixture of an alcohol and water, a mixture of an alcohol,water, and gasoline, etc as a second substance. In still anotherexample, the first substance may be a gasoline alcohol blend with alower alcohol concentration than a gasoline alcohol blend of a secondsubstance. In yet another example, the first substance may be gasolineor diesel fuel, and the second substance may be a dimethyl ether, amethyl ester, a lower alkyl alcohol (such as methanol, ethanol,propanol, or butanol), or a mixture thereof.

In another embodiment, different injector locations may be used fordifferent substances. For example, a single injector (such as a directinjector) may be used to inject a mixture of two substances (e.g.,gasoline and an alcohol/water mixture), where the relative amount orratio of the two or more fuel quantities or substances in the mixturemay be varied during engine operation via adjustments made by controller6 via a mixing valve (not shown), for example. In still another example,two different injectors for each cylinder are used, such as port anddirect injectors, each injecting a different substance in differentrelative amounts as operating conditions vary. In even anotherembodiment, different sized injectors, in addition to differentlocations and different substances, may be used. In yet anotherembodiment, two port injectors with different spray patterns and/or aimpoints may be used.

Various advantageous results may be obtained by various of the abovesystems. For example, when using both gasoline and a fuel having alcohol(e.g., ethanol), it may be possible to adjust the relative amounts ofthe fuels to take advantage of the increased charge cooling of alcoholfuels (e.g., via direct injection) to reduce the tendency of knock(e.g., in response to knock or increased load, increasing a relativeamount of alcohol and/water). This phenomenon, combined with increasedcompression ratio, and/or boosting and/or engine downsizing, can then beused to obtain large fuel economy benefits (by reducing the knocklimitations on the engine), while allowing engine operation on gasolineat lighter loads when knock is not a constraint. The knock suppressionbenefits offered by this phenomenon may be significantly larger than thebenefits offered by the dual injection of hydrocarbon fuels withdifferent octane ratings. However, when combusting a mixture havingalcohol, the likelihood of pre-ignition may be increased under certainoperating conditions. As such, in one example, by utilizing waterinstead of or mixed into the substance having alcohol, it may bepossible to reduce the likelihood of pre-ignition, while still takingadvantage of increased charge cooling effects and the availability ofalcohol containing fuels.

Additional details of engine, transmission, and/or vehicle controlapproaches are described herein, as well as in U.S. patent applicationSer. No. 11/384,111, titled “CONTROL FOR KNOCK SUPPRESSION FLUIDSEPARATOR IN A MOTOR VEHICLE”, by Thomas G. Leone, Attorney Docket81138701, filed Mar. 17, 2006, the entire contents of which areincorporated herein by reference for all purposes.

Referring now to FIG. 2, it shows one cylinder of a multi-cylinderengine, as well as the intake and exhaust path connected to thatcylinder. Further, FIG. 2 shows one example fuel system with two fuelinjectors per cylinder, for at least one cylinder. In one embodiment,each cylinder of the engine may have two fuel injectors. The twoinjectors may be configured in various locations, such as two portinjectors, one port injector and one direct injector (as shown in FIG.2), or others.

Also, as described herein, there are various configurations of thecylinders, fuel injectors, and exhaust system, as well as variousconfigurations for the fuel vapor purging system and exhaust gas oxygensensor locations.

Continuing with FIG. 2, it shows a multiple injection system, whereengine 10 has both direct and port fuel injection, as well as sparkignition. Internal combustion engine 10, comprising a plurality ofcombustion chambers, is controlled by electronic engine controller 12.Combustion chamber 30 of engine 10 is shown including combustion chamberwalls 32 with piston 36 positioned therein and connected to crankshaft40. A starter motor (not shown) may be coupled to crankshaft 40 via aflywheel (not shown), or alternatively direct engine starting may beused.

In one particular example, piston 36 may include a recess or bowl (notshown) to help in forming stratified charges of air and fuel, ifdesired. However, in an alternative embodiment, a flat piston may beused.

Combustion chamber, or cylinder, 30 is shown communicating with intakemanifold 44 and exhaust manifold 48 via respective intake valves 52 aand 52 b (not shown), and exhaust valves 54 a and 54 b (not shown).Thus, while four valves per cylinder may be used, in another example, asingle intake and single exhaust valve per cylinder may also be used. Instill another example, two intake valves and one exhaust valve percylinder may be used.

Combustion chamber 30 can have a compression ratio, which is the ratioof volumes when piston 36 is at bottom center to top center. In oneexample, the compression ratio may be approximately 9:1. However, insome examples where different fuels are used, the compression ratio maybe increased. For example, it may be between 10:1 and 11:1 or 11:1 and12:1, or greater.

Fuel injector 66A is shown directly coupled to combustion chamber 30 fordelivering injected fuel directly therein in proportion to the pulsewidth of signal dfpw received from controller 12 via electronic driver68A. While FIG. 2 shows injector 66A as a side injector, it may also belocated overhead of the piston, such as near the position of spark plug92. Such a position may improve mixing and combustion due to the lowervolatility of some alcohol based fuels. Alternatively, the injector maybe located overhead and near the intake valve to improve mixing.

Fuel and/or water may be delivered to fuel injector 66A by a highpressure fuel system (not shown) including a fuel tank, fuel pumps, anda fuel rail. Alternatively, fuel and/or water may be delivered by asingle stage fuel pump at lower pressure, in which case the timing ofthe direct fuel injection may be more limited during the compressionstroke than if a high pressure fuel system is used. Further, while notshown, the fuel tank (or tanks) may (each) have a pressure transducerproviding a signal to controller 12.

Fuel injector 66B is shown coupled to intake manifold 44, rather thandirectly to cylinder 30. Fuel injector 66B delivers injected fuel inproportion to the pulse width of signal pfpw received from controller 12via electronic driver 68B. Note that a single driver 68 may be used forboth fuel injection systems, or multiple drivers may be used. Fuelsystem 164 is also shown in schematic form delivering vapors to intakemanifold 44, where fuel system 164 is also coupled to injectors 66A and66B (although not shown in this Figure). Various fuel systems and fuelvapor purge systems may be used.

Intake manifold 44 is shown communicating with throttle body 58 viathrottle plate 62. In this particular example, throttle plate 62 iscoupled to electric motor 94 so that the position of elliptical throttleplate 62 is controlled by controller 12 via electric motor 94. Thisconfiguration may be referred to as electronic throttle control (ETC),which can also be utilized during idle speed control. In an alternativeembodiment (not shown), a bypass air passageway is arranged in parallelwith throttle plate 62 to control inducted airflow during idle speedcontrol via an idle control by-pass valve positioned within the airpassageway.

Exhaust gas sensor 76 is shown coupled to exhaust manifold 48 upstreamof catalytic converter 70 (where sensor 76 can correspond to variousdifferent sensors). For example, sensor 76 may be any of many knownsensors for providing an indication of exhaust gas air/fuel ratio suchas a linear oxygen sensor, a UEGO, a two-state oxygen sensor, an EGO, aHEGO, or an HC or CO sensor. In this particular example, sensor 76 is atwo-state oxygen sensor that provides signal EGO to controller 12 whichconverts signal EGO into two-state signal EGOS. A high voltage state ofsignal EGOS indicates exhaust gases are rich of stoichiometry and a lowvoltage state of signal EGOS indicates exhaust gases are lean ofstoichiometry. Signal EGOS may be used to advantage during feedbackair/fuel control to maintain average air/fuel at stoichiometry during astoichiometric homogeneous mode of operation. Further details ofair-fuel ratio control are included herein.

Distributorless ignition system 88 provides ignition spark to combustionchamber 30 via spark plug 92 in response to spark advance signal SA fromcontroller 12.

Controller 12 may cause combustion chamber 30 to operate in a variety ofcombustion modes, including a homogeneous air/fuel mode and/or astratified air/fuel mode by controlling injection timing, injectionamounts, spray patterns, etc. Further, combined stratified andhomogenous mixtures may be formed in the chamber. In one example,stratified layers may be formed by operating injector 66A during acompression stroke. In another example, a homogenous mixture may beformed by operating one or both of injectors 66A and 66B during anintake stroke (which may be open valve injection). In yet anotherexample, a homogenous mixture may be formed by operating one or both ofinjectors 66A and 66B before an intake stroke (which may be closed valveinjection). In still other examples, multiple injections from one orboth of injectors 66A and 66B may be used during one or more strokes(e.g., intake, compression, exhaust, etc.). Even further examples may bewhere different injection timings and mixture formations are used underdifferent conditions, as described below.

Controller 12 can control the amount of fuel delivered by fuel injectors66A and 66B so that the homogeneous, stratified, or combinedhomogenous/stratified air/fuel mixture in chamber 30 can be selected tobe at stoichiometry, a value rich of stoichiometry, or a value lean ofstoichiometry.

While FIG. 2 shows two injectors for the cylinder, one being a directinjector and the other being a port injector, in an alternativeembodiment two port injectors for the cylinder may be used, along withopen valve injection, for example.

Emission control device 72 is shown positioned downstream of catalyticconverter 70. Emission control device 72 may be a three-way catalyst ora NOx trap, or combinations thereof.

Controller 12 is shown as a microcomputer, including microprocessor unit102, input/output ports 104, an electronic storage medium for executableprograms and calibration values shown as read only memory chip 106 inthis particular example, random access memory 108, keep alive memory110, and a conventional data bus. Controller 12 is shown receivingvarious signals from sensors coupled to engine 10, in addition to thosesignals previously discussed, including measurement of inducted mass airflow (MAF) from mass air flow sensor 100 coupled to throttle body 58;engine coolant temperature (ECT) from temperature sensor 112 coupled tocooling sleeve 114; a profile ignition pickup signal (PIP) from Halleffect sensor 118 coupled to crankshaft 40; and throttle position TPfrom throttle position sensor 120; absolute Manifold Pressure Signal MAPfrom sensor 122; an indication of knock from knock sensor 182; and anindication of absolute or relative ambient humidity from sensor 180.Engine speed signal RPM is generated by controller 12 from signal PIP ina conventional manner and manifold pressure signal MAP from a manifoldpressure sensor provides an indication of vacuum, or pressure, in theintake manifold. During stoichiometric operation, this sensor can givean indication of engine load. Further, this sensor, along with enginespeed, can provide an estimate of charge (including air) inducted intothe cylinder. In one example, sensor 118, which is also used as anengine speed sensor, produces a predetermined number of equally spacedpulses every revolution of the crankshaft.

Continuing with FIG. 2, a variable camshaft timing system is shown.Specifically, camshaft 130 of engine 10 is shown communicating withrocker arms 132 and 134 for actuating intake valves 52 a, 52 b andexhaust valves 54 a, 54 b. Camshaft 130 is directly coupled to housing136. Housing 136 forms a toothed wheel having a plurality of teeth 138.Housing 136 is hydraulically coupled to crankshaft 40 via a timing chainor belt (not shown). Therefore, housing 136 and camshaft 130 rotate at aspeed substantially equivalent to the crankshaft. However, bymanipulation of the hydraulic coupling as will be described laterherein, the relative position of camshaft 130 to crankshaft 40 can bevaried by hydraulic pressures in advance chamber 142 and retard chamber144. By allowing high pressure hydraulic fluid to enter advance chamber142, the relative relationship between camshaft 130 and crankshaft 40 isadvanced. Thus, intake valves 52 a, 52 b and exhaust valves 54 a, 54 bopen and close at a time earlier than normal relative to crankshaft 40.Similarly, by allowing high pressure hydraulic fluid to enter retardchamber 144, the relative relationship between camshaft 130 andcrankshaft 40 is retarded. Thus, intake valves 52 a, 52 b, and exhaustvalves 54 a, 54 b open and close at a time later than normal relative tocrankshaft 40.

While this example shows a system in which the intake and exhaust valvetiming are controlled concurrently, variable intake cam timing, variableexhaust cam timing, dual independent variable cam timing, or fixed camtiming may be used. Further, variable valve lift may also be used.Further, camshaft profile switching may be used to provide different camprofiles under different operating conditions. Further still, thevalvetrain may be roller finger follower, direct acting mechanicalbucket, electromechanical, electrohydraulic, or other alternatives torocker arms.

Continuing with the variable cam timing system, teeth 138, being coupledto housing 136 and camshaft 130, allow for measurement of relative camposition via cam timing sensor 150 providing signal VCT to controller12. Teeth 1, 2, 3, and 4 are preferably used for measurement of camtiming and are equally spaced (for example, in a V-8 dual bank engine,spaced 90 degrees apart from one another) while tooth 5 is preferablyused for cylinder identification, as described later herein. Inaddition, controller 12 sends control signals (LACT, RACT) toconventional solenoid valves (not shown) to control the flow ofhydraulic fluid either into advance chamber 142, retard chamber 144, orneither.

Relative cam timing can be measured in a variety of ways. In generalterms, the time, or rotation angle, between the rising edge of the PIPsignal and receiving a signal from one of the plurality of teeth 138 onhousing 136 gives a measure of the relative cam timing. For theparticular example of a V-8 engine, with two cylinder banks and afive-toothed wheel, a measure of cam timing for a particular bank isreceived four times per revolution, with the extra signal used forcylinder identification.

Sensor 160 may also provide an indication of oxygen concentration in theexhaust gas via signal 162, which provides controller 12 a voltageindicative of the O2 concentration. For example, sensor 160 can be aHEGO, UEGO, EGO, or other type of exhaust gas sensor. Also note that, asdescribed above with regard to sensor 76, sensor 160 can correspond tovarious different sensors.

As described above, FIG. 2 merely shows one cylinder of a multi-cylinderengine, and it is understood that each cylinder has its own set ofintake/exhaust valves, fuel injectors, spark plugs, etc.

Also, in the example embodiments described herein, the engine may becoupled to a starter motor (not shown) for starting the engine. Thestarter motor may be powered when the driver turns a key in the ignitionswitch on the steering column, for example. The starter is disengagedafter engine starting, for example, by engine 10 reaching apredetermined speed after a predetermined time.

Continuing with FIG. 2, an exhaust gas recirculation system is shown.Exhaust gas is delivered to intake manifold 44 by a conventional EGRtube 172 communicating with exhaust manifold 48, EGR valve assembly 174,and EGR orifice 176. Alternatively, tube 172 could be an internallyrouted passage in the engine that communicates between exhaust manifold48 and intake manifold 44. As will be described in further detailherein, EGR tube 172 (or another EGR tube or a branch (not shown) of EGRtube 172) may be configured to assist the fuel system in the separationof a mixed fuel.

As noted above, engine 10 may operate in various modes, including leanoperation, rich operation, and “near stoichiometric” operation. “Nearstoichiometric” operation can refer to oscillatory operation around thestoichiometric air fuel ratio. Typically, this oscillatory operation isgoverned by feedback from exhaust gas oxygen sensors. In this nearstoichiometric operating mode, the engine may be operated withinapproximately one air-fuel ratio of the stoichiometric air-fuel ratio.

Feedback air-fuel ratio control may be used for providing the nearstoichiometric operation. Further, feedback from exhaust gas oxygensensors can be used for controlling air-fuel ratio during lean andduring rich operation. In particular, a switching type, heated exhaustgas oxygen sensor (HEGO) can be used for stoichiometric air-fuel ratiocontrol by controlling fuel injected (or additional air via throttle orVCT) based on feedback from the HEGO sensor and the desired air-fuelratio. Further, a ULEGO sensor (which provides a substantially linearoutput versus exhaust air-fuel ratio) can be used for controllingair-fuel ratio during lean, rich, and stoichiometric operation. In thiscase, fuel injection (or additional air via throttle or VCT) can beadjusted based on a desired air-fuel ratio and the air-fuel ratio fromthe sensor. Further still, individual cylinder air-fuel ratio controlcould be used, if desired. Adjustments may be made with injector 66A,66B, or combinations thereof depending on various factors, to controlengine air-fuel ratio.

Also note that various methods can be used to maintain the desiredtorque such as, for example, adjusting ignition timing, throttleposition, variable cam timing position, exhaust gas recirculationamount, and number of cylinders carrying out combustion. Further, thesevariables can be individually adjusted for each cylinder to maintaincylinder balance among all the cylinders. While not shown in FIG. 2,engine 10 may be coupled to various boosting devices, such as asupercharger or turbocharger. On a boosted engine, desired torque mayalso be maintained by adjusting wastegate and/or compressor bypassvalves.

Referring now to FIG. 3, an example fuel system layout is provided withfuel tank 310 having fuel fill cap 312. The system is configured toreceive a fuel mixture through the fill line 314 and into tank 310,where the mixture may be a gasoline/alcohol mixture, agasoline/alcohol/water mixture, or various others such as noted herein,including, a gasoline/ethanol mixture such as E10, for example. The fuelmixture in tank 310 may be transported to a separator system 320 via atransport system, shown by double arrow 316. The transport system 316may be a one way transport, e.g., transporting the fuel mixture to theseparator 320, or may enable two-way transportation, such as returnlines from the separator or downstream fuel system back to the tank 310.The transport system 316 may include pumps, valves, multiple separatelines, or various other components, such as described below herein withregard to example systems. Further, while FIG. 3 shows the transportsystem 316 external to tank 310, system 316 along with separator 320and/or portions of transport system 322 may also be located within or atleast partially within tank 310.

Continuing with FIG. 3, it also shows downstream transport system 322located between separator 320 and the engine (not shown). Transportsystem 322 is shown having at least two separate lines coupled to theseparator to transport different amounts of substances or fuels withdifferent constituents to the engine depending on operating conditions.Transport system 322 may maintain the different fuels separate indelivering the fuels to the engine, or may mix the fuels for co-deliveryto the engine, as illustrated in FIG. 3. Further, like system 316,system 322 may include pumps, valves, multiple separate lines, returnlines, or various other components, such as described below herein withregard to example systems.

Separator system 320 is configured to allow two or more components inthe fuel mixture stored in tank 310 to be separated and providedseparately to engine 10, thereby permitting the advantages of dual ormixed injection strategies to be employed without causing inconvenienceto a user.

FIG. 4 illustrates one exemplary embodiment of a method 400 of operatingengine 10 via a fuel separation/mixed injection strategy. First, method400 includes inputting a mixed fuel into tank 310, or receiving themixed fuel into the tank. In the embodiment of FIG. 4, the mixed fuelcontains a hydrocarbon component (such as gasoline) and an alcoholcomponent (including but not limited to ethanol or methanol). However,it will be appreciated that any suitable mixed fuel may be used,including but not limited to other polar and/or oxygenated fuels such asethers and esters and other nonpolar and/or hydrocarbon fuels such asdiesel.

Next, method 400 includes separating, at 404, the mixed fuel into ahydrocarbon-enriched fraction and an alcohol-enriched fraction. As usedherein, the terms “hydrocarbon-enriched” refers to the volume of fuelafter separation from which either the alcohol was removed, or thevolume of fuel containing hydrocarbons removed from the mixed fuel,depending upon whether the separator is configured to extract thehydrocarbon or alcohol components. Likewise, the term “alcohol-enriched”refers to the volume of fuel after separation from which either thehydrocarbon was removed, or the volume of fuel containing alcohols (orother oxygenated or polar fuels) removed from the hydrocarbon portion ofthe mixed fuel, depending upon the separation mechanism employed. Itwill be appreciated that the relative concentrations of the alcohol andhydrocarbon components of the “hydrocarbon-enriched” or“alcohol-enriched” fractions may be either higher or lower than theother respective component of those fractions. Furthermore, the term“fraction” is used herein merely to denote a volume of fuel after aseparation process, and does not imply that any particular type ofseparation process is employed.

After separating the mixed fuel into at least the alcohol-enriched andhydrocarbon-enriched fractions, method 400 next includes controlling theprovision of fuel from the alcohol-enriched fraction and fuel from thehydrocarbon-enriched fraction to engine 10 based upon an engineoperating condition. For example, if engine knock is detected, a greaterrelative amount of fuel from the alcohol-enriched fraction may beprovided to reduce knock. Furthermore, in a fuel system with more thantwo inputs, water may be added from a third input to help preventpre-ignition. Alternatively, the alcohol-enriched fraction may contain aquantity of water to help prevent pre-ignition. As another example, agreater relative amount of fuel from the hydrocarbon-enriched fractionmay be provided to the engine as an engine load increases, therebyproviding a greater amount of energy to the engine. It will beappreciated that these are merely exemplary methods of controlling theprovision of the alcohol-enriched fuel fraction and thehydrocarbon-enriched fuel fraction to engine 10, and that the relativeamounts (or ratio) of fuels from these fractions may be adjusted basedupon any other suitable engine operating conditions or for any othersuitable purpose. Other examples include, but are not limited to, thereduction of emissions and/or the enhancement of fuel economy.

Any suitable methods and/or structures may be used to separate a mixedfuel in a fuel system according to the present disclosure. For example,in some embodiments, an aqueous extraction may be used to remove fuelcomponents soluble in water (such as methanol, ethanol, etc.) from fuelcomponents not soluble in water. FIG. 5 shows, generally at 500, anexemplary embodiment of a fuel system having an aqueous extractionsystem for separating an alcohol (or other polar fuel component) from ahydrocarbon fuel component. Fuel system 500 includes a fuel tank 510 forreceiving a fuel input by a user, and an extraction tank 520 in fluidiccommunication with and configured to receive mixed fuel from tank 510.As used herein, the term “in fluidic communication with” (and variationsthereof) refers to the existence of a fluid path between components, andneither implies nor excludes the existence of any intermediatestructures or components, nor implies that a path is always open oravailable for fluid flow.

Fuel system 500 also includes an extraction fluid source 522 in fluidcommunication with extraction tank 520 for the extraction of a fuelcomponent from the mixed fuel. Extraction fluid source may be configuredto provide any suitable extraction fluid to extraction tank 520 in anysuitable manner. Suitable extraction fluids include those fluids whichare miscible with the component or components of the mixed fuel to beextracted and are immiscible with the component or components of themixed fuel not to be extracted. Where the mixed fuel contains a loweralkyl alcohol and gasoline, an example of a suitable extraction fluid iswater. In one embodiment, extraction fluid source 522 includes a holdingtank to which water may be periodically added, for example, by a user orduring a vehicle servicing. Alternatively, extraction fluid source 522may include a condenser that condenses water vapor from air, exhaust,etc. For example, a collector may be located within or coupled to anair-conditioning unit in order to collect condensed water.

Extraction tank 520 may include a mixer or agitator (depictedschematically at 524) to ensure that the extraction fluid and mixed fuelare well mixed for the extraction process. Alternatively, extractiontank 520 may not include a mixer, and instead may rely on momentumchanges in driving (for example, hitting bumps,acceleration/deceleration, etc.) to help mix the extraction fluid andthe mixed fuel. Furthermore, in an alternative embodiment, extractionfluid may be added to the mixed fuel in a conduit that is upstream fromand leads to the extraction tank. The fluids may mix while flowing inthe conduit and upon entering the extraction tank 520. In either ofthese embodiments, after mixing, the fluids may be allowed to separatewhile in the extraction tank. After mixing, the aqueous phase containingthe alcohol-enriched fraction settles to the bottom of extraction tank520 and the hydrocarbon-enriched fraction rises to the top of thealcohol-enriched fraction. To separate the two fractions, a first outletfor the alcohol-enriched fraction may be provided at a location inextraction tank 520 at a level above the border between thealcohol-enriched fraction and the hydrocarbon-enriched fraction to allowthe hydrocarbon-enriched fraction to be removed, and a second outlet maybe provided at a level below this border (for example, at the bottom ofextraction tank 520) to allow the alcohol-enriched fraction to beremoved.

After removal from extraction tank 520, either or both of thehydrocarbon-enriched fraction and the alcohol-enriched fraction may bestored in a storage tank (shown at 530 a and 530 b, respectively) beforebeing provided to engine 10. Alternatively, either or both of thehydrocarbon-enriched fraction and the alcohol-enriched fraction may beprovided directly to engine, without storage in a storage tank, viainjectors 66A, 66B or via intake manifold 44. A sensor 540 may beprovided in communication with controller 12 to output a signalproportional to an amount of alcohol present in the extraction fluid.From this signal, controller 12 may determine a calorie content per unitvolume of the alcohol-enriched fraction for use in controlling theaddition of the two fuel fractions to the engine. Suitable sensors foruse as sensor 540 include, but are not limited to, refractive indexsensors.

As one example, the relative amounts of separate substances delivered tothe engine may be varied depending on the composition of thehydrocarbon-enriched fraction and the alcohol-enriched fractiongenerated by the separator. In this, it may be possible to provideconsistent levels of knock reduction while also providing desired enginetorque, thus compensating for variation in caloric content and knocksuppression effectiveness.

FIG. 6 shows, generally at 600, another exemplary embodiment of a fuelsystem and separator. Fuel system 600 includes a fuel tank 610, aseparator 620, a first fuel fraction storage tank 630 a, a second fuelfraction storage tank 630 b, and a condenser 640. Fuel system 600 alsoincludes an exhaust gas recirculation (EGR) tube 650 configured torecirculate exhaust gases from the engine exhaust manifold 48 intoseparator 620. Exhaust gas recirculation tube 650 may be the same asexhaust gas recirculation tube 170 shown in FIG. 2, or may be a separatetube or a branch of tube 170.

Separator 620 includes a barrier 622 separating a first passageway 624from a second passageway 626. Barrier 622 is made at least partially ofa material or materials that selectively transports one component of themixed fuel at a higher rate than, or even to the substantial exclusionof, the other component of the mixed fuel. The extracted fuel componentcrosses barrier 622 into second passageway 626, while the unextractedfuel components remain in first passageway 624. In this manner, a firstfuel fraction (either hydrocarbon-enriched or alcohol-enriched,depending upon whether the materials used for barrier 622 selectivelypass hydrocarbons or alcohols) may be collected at the outlet of firstpassageway, and a second fuel fraction may be collected at the outlet ofthe second passageway. The recirculated exhaust gases provided byexhaust gas recirculation tube 650 may be directed to flow across theopposite side of barrier 622 as the mixed fuel input, therebytransporting fuel components that diffuse through barrier 622 away frombarrier 622. This may improve the rate of fuel transport across thebarrier. Furthermore, the recirculated exhaust gas also may be used toheat the separator, which may also help to drive the pervaporation ofthe extracted fuel component across the membrane, thereby increasingfuel transport rates across barrier 622.

Condenser 640 may be used to condense the extracted fuel component outof the recirculated exhaust gas stream after pervaporation, along withwater vapor and any other condensable exhaust components. The condensedextracted fuel may then be collected in first fuel fraction storage tank630 a for later use by engine 10. The recirculated exhaust gases mayalso be provided to an intake manifold of engine 10 as shown in FIG. 6,or may be emitted from the engine as exhaust. It will be appreciatedthat the recirculated exhaust gas may be directed through othercomponents either before or after flowing through the separator. Oneexample of such other components is an EGR cooler, which may bepositioned either upstream or downstream of separator 620.

Barrier 622 may be formed from any suitable material or materials.Suitable materials include materials that selectively pass one type offuel within the mixed fuel to the exclusion or substantial exclusion ofthe other type or types of fuels in the mixed fuel, that pass one typeof fuel at a higher rate than the other types of fuels, or that possessany other property that allows the enrichment of a selected fuel typewithin the mixed fuel. Selectivity may be based upon any suitabledifferences in physical properties between the desired fuel components.Examples include, but are not limited to, relative polarities of thefuel components, chemical reactivity and/or surface absorptioncharacteristics of the fuel components with the surfaces of theselective material, the molecular size of the fuel components relativeto a pore size of the selective material, and combinations of theseproperties.

In one embodiment, the barrier 622 comprises a material with a chemicalor physical affinity for a selected fuel component in the mixed fuel.For example, where the mixed fuel includes ethanol (or other loweralcohol) and gasoline, a polymeric material with an affinity for polarmolecules may be used to selectively transport the ethanol molecules tothe substantial exclusion of hydrocarbons. Examples of suitable polymermaterials with selectivity for lower alcohols such as methanol, ethanoland propanol include, but are not limited to, polyvinyl alcohol,polysulfone, poly(ether ether ketone), polydimethyl siloxane, andcellulose triacetate. These materials may show selective transport overpolar molecules over the hydrocarbon components of gasoline, which tendto show more nonpolar behavior. Such materials may also be effective inselectively transporting other oxygenated or polar fuel components thatmay be used in a mixed fuel, such as ethers and esters. In someembodiments, the polymer material may be supported by a ceramic, metalor other rigid support on which the polymer is deposited as a thin orthick film. In other embodiments, the polymer material may comprise thebulk of the selective barrier.

In another embodiment, selective barrier 622 may include a material thatselectively passes a lower alcohol component of a mixed fuel over ahydrocarbon component based upon size selectivity. The smallest majoritycomponents in gasoline may include isooctane and heptane, and othersmall components found in lower concentrations may include branched andcyclic hexanes, pentane and butane. In comparison, ethanol is smallerthan these hydrocarbons. Therefore, a porous material such as a zeoliteor other porous metal oxide, or even porous metals, may be used totransport the smaller ethanol molecule at a higher rate than the largerhydrocarbons. Any suitable porous material may be used. In one specificembodiment, zeolite-Y may be used. Furthermore, the pores of the metaloxide may be chemically modified to change or enhance the selectivetransport properties of the material. For example, where the porousmaterial is a zeolite, ion exchange may be used to increase the polarityand/or modify the acidity within the pores to enhance the transport ofalcohols through the material. Likewise, if it desired to extract thehydrocarbons, rather than alcohols, from a mixed fuel, an alkyl siloxaneor other siloxane having organic functional groups may be chemicallyreacted with the silicon oxide sites within the zeolite pores. In thismanner, the siloxy groups of the organic siloxane may chemically bond tothe zeolite within the pores, and the organic functional groups form anonpolar surface, thereby allowing nonpolar molecules to diffuse throughthe material while inhibiting the transport of polar materials. Such asurface modification may also be used to decrease an amount of thetransported fuel component that remains adsorbed to the surfaces of thepores, rather than being transported through the pores. Likewise, thepores may be coated with a polymer material that has an affinity foreither the polar or nonpolar components of the mixed fuel. Examples ofpolymer coatings that may enhance the selectivity of a material to passan alcohol to the substantial exclusion of a nonpolar hydrocarboninclude, but are not limited to, polyvinylalcohol, polydimethylsiloxane, poly (amide-b-ether) copolymer, polyether sulfone, and poly(ether ketone). It will be appreciated that these are merely examples ofpotential porous materials and modifications that can be made to theporous materials, and that any other suitable materials and/or materialmodifications may be used.

Separator 620 may have any suitable configuration for performing theseparation of the mixed fuel. FIG. 7 shows, generally at 720, oneexemplary embodiment of a suitable separator configuration. Separator720 includes an inner passageway 724 defined by a selective barrier 722,and an outer passageway 726 defined by an outer wall 728. Innerpassageway 724 may be configured to receive a flow of mixed fuel from afuel tank. As illustrated by the arrows in FIG. 7, the extractedcomponent of the mixed fuel is transported across the membrane from theinner passageway to the outer passageway.

Inner passageway 724 may include a restriction 730 or narrowing to slowfluid flow through inner passageway 724 and to increase the pressure ofthe mixed fuel on the selective barrier 722. This may help to improvetransport rates and recovery yields of the extracted fuel component.Additionally, pumps and/or other components may be used to provideadditional pressure control to optimize the pressure of the mixed fuelin the separator to promote transport of the desired fuel componentacross the selective barrier. Such systems may allow the pressure beadjusted from atmospheric pressure (ambient pressure) to severalthousand pounds per square inch.

The extracted fuel component may be recovered in outer passageway 728 asa liquid, or as a gas where barrier 722 is a pervaporation membrane.Where the extracted fuel component is recovered as a gas, it may beconverted to a liquid phase for storage in a condenser as illustrated inFIG. 6, or may be provided to an injector or intake manifold in the gasphase without condensation. Furthermore, as illustrated in FIG. 6,recirculated exhaust gas may be directed through outer passageway 728 toheat separator 720 and/or to help collect extracted fuel components,thereby increasing fuel transport rates through selective barrier 722.Alternatively, another extraction fluid, such as water from a storagereservoir or condenser, may be flowed through outer passageway 728 tocollect the extracted fuel component and to help increase transportrates. In these embodiments, the water or other extraction fluid may beheated before passing through separator 720, or separator 720 may beheated from another source (for example, an electrical heater orrecirculated exhaust gas flowed around the exterior of separator 720).

The recirculated exhaust gases (or other extraction fluid) may be passedthrough outer passageway 728 in a direction opposite the flow of themixed fuel through inner passageway 724 as illustrated in FIG. 7, or maybe flowed through in a similar direction. Furthermore, in an alternateembodiment, the mixed fuel may be provided to outer passageway 728, andthe recirculated exhaust gas or other extraction fluid may be providedto the inner passageway. In these embodiments, outer passageway 728 mayinclude a restriction to slow the flow of the mixed fuel and to increasethe pressure of the mixed fuel on selective barrier 722. The restrictionmay be adjustable in diameter, circumference and/or cross-sectional areato allow the pressure of the mixed fuel on the selective barrier 722 tobe adjusted as desired.

FIG. 8 shows another exemplary embodiment of a separator, generally at820. Instead of having a single tubular selective barrier surrounded byan outer wall, separator 820 includes a plurality of tubular selectivebarriers 822 defining a plurality of inner passageways. The plurality oftubular barriers 822 are contained within a single tubular outer wall824, which defines a single outer passageway. A first input 826 isprovided for flowing a fluid through the plurality of tubular barriers822, and a second input 828 is provided for flowing a fluid through theinterior of tubular outer wall 824 and around the exteriors of theplurality of tubular inner barriers 822. In this manner, the surfacearea of the selective transport barrier may be increased relative to theembodiment of FIG. 6. Examples of such extraction systems includewater-permeable selective barriers sold under the trade name PERMAPUREby Permapure, LLC of Toms River, N.J.

FIG. 9 shows another exemplary embodiment of a separator, generally at920. Separator 920 includes a selective barrier 922 and an outer wall924 that divides an interior defined by the outer wall into a firstpassageway 926 and a second passageway 928. Selective barrier 922 takesthe form of a linear membrane disposed across the interior of outer wall924. Mixed fuel may be provided to one of first passageway 926 andsecond passageway 928, and an extracted fuel component may be recoveredfrom the other of first passageway 926 and 928. Depending upon thematerial used for selective barrier 922, selective barrier 922 mayinclude a rigid support material (for example, a metal or ceramicmaterial) that supports the selective barrier material. Such a rigidbarrier material may help to support the selective barrier materialagainst elevated pressures that may be used in the fuel separationprocess. In other embodiments, the selective barrier material may besufficiently strong and rigid to allow the omission of a support.

FIG. 10 shows another exemplary embodiment of a separator, generally at1020. Separator 1020 is similar to the other embodiments described abovein that it includes a selective barrier 1022 and an outer wall 1024 thatdivides an interior defined by the outer wall into a first passageway1026 and a second passageway 1028. However, selective barrier 1022 takesthe form of a folded or pleated barrier, instead of a linear barrier.Mixed fuel may be provided to one of first passageway 1026 and secondpassageway 1028, and an extracted fuel component may be recovered fromthe other of first passageway 1026 and 1028. The use of a folded orpleated barrier as opposed to a linear barrier may help to increase thesurface area of the selective barrier, and therefore may help toincrease fuel separation rates. It will be appreciated that a folded orpleated barrier may also be used in conjunction with a tubular barrierstructure such as those shown in the embodiments of FIGS. 7 and 8.

FIG. 11 shows another exemplary embodiment of a separator, generally at1120. Separator 1120 includes a selective barrier 1122, an outer wall1124, and a first passageway 1126 and second passageway 1128 separatedby the selective barrier. Separator 1120 also includes a first electrode1130 and second electrode 1132 positioned on opposite sides of selectivebarrier 1122. Furthermore, selective barrier 1122 may be made at leastpartially of an ionically or electrically conductive polymeric orinorganic material, polypyrole being one example of a conductivepolymer. A voltage and/or current may be applied across and/or throughthe membrane using a voltage and/or current supply 1134, respectively.In this embodiment, an ionic current could be induced across a membraneusing the polarizable properties of an alcohol moiety. Furthermore, thehydroxide functional group may be induced to give up a proton duringtransport, creating an oxyanion that would be selectively transported bypolar interaction with cationic functional groups on the surface andinterior of the porous membrane material, and/or by the motion of thecharged ethoxy anion in response to the applied electric field. In thedepicted embodiment, electrodes 1130 and 1132 are shown as coveringsubstantially the entire lower and upper surfaces of selective barrier1122, respectively. However, it will be appreciated that electrodes ofany suitable configuration and/or placement may be used toelectrochemically or electrophoretically move a selected mixed fuelspecies across a selective membrane.

FIG. 12 shows another exemplary embodiment of a fuel system, generallyat 1200. Fuel system 1200 includes a fuel tank 1210, a fuel separator1220, and first and second fuel fraction storage tanks for storing theenriched fuel fractions after separation and before provision to engine10. Fuel system 1200 also includes an extraction fluid storage tank 1240and a separator heater 1250. This is in contrast to the above-describedembodiments where recirculated exhaust gases are utilized as anextraction fluid and as a heat source for heating the separator. Anysuitable fluid may be used as the extraction fluid. For example, in someembodiments, the extraction fluid may comprise water that is eitheradded to storage tank 1240 by a user on a periodic or occasional basis,and/or may comprise a condenser that is configured to condense watervapor from air to collect water for use as an extraction fluid.Furthermore, extraction fluid storage tank 1240 may comprise a storagetank conventionally utilized in vehicles for storing aqueous fluids. Forexample, in one embodiment, fluid storage tank 1240 comprises awindshield washer fluid tank from which fluid is drawn for washing avehicle windshield and for extracting/removing the transported fuelcomponent from separator 1220 after fuel separation.

Heater 1250 may optionally be utilized where it is desired to heat theseparator, for example, to improve the transport rate of the desiredfuel component across the selective barrier, and/or to cause theseparated fuel component to be recovered in the gas phase in separator1220 (i.e. to utilize a pervaporation separation). Any suitable heatsource may be used as heater 1250. Examples include, but are not limitedto, electric heaters, radiative heating from the engine, recirculatedexhaust gases, and/or combinations of these heat sources.

FIG. 13 shows another exemplary embodiment of a fuel system, generallyat 1300. Fuel system 1300 includes a fuel tank 1310, a fuel separator1320, an exhaust gas recirculation system 1340 for heating the separatorand/or recovering the extracted fuel species from the separator.However, fuel system 1300 includes only a single fuel fraction storagetank 1330, instead of two fuel fraction storage tanks. The other fuelfraction (for example, a pervaporated fuel fraction carried by therecirculated exhaust gas) is instead provided directly to engine 10,without condensation and storage. This fuel fraction may be provided toa direct injector, port injector, and/or intake manifold. It will beappreciated that various structures for controlling the flow of the gasphase fuel fraction into engine 10 may be utilized, including but notlimited to a fuel pump, fuel rail, sensors for detecting a caloriecontent of the gaseous mixture, pressure sensors, etc.

FIG. 14 shows yet another exemplary embodiment of a fuel system,generally at 1400. Fuel system 1400 includes a fuel tank 1410, aseparator 1420, and an exhaust gas recirculation system 1440 for heatingthe separator and/or recovering the extracted fuel species from theseparator. However, fuel system 1440 does not include fuel fractionstorage tanks disposed between the separator and engine 10. Instead,both fuel fractions are provided directly to the engine. Either or bothfuel fractions may be provided to any suitable injector and/or may beprovided directly to the intake manifold as a gaseous mixture wheresuitable.

As mentioned above, where the selective barrier utilizes pervaporationor produces a vaporous mixture of fuel as a product of the extraction,the fuel vapor may be delivered directly to a gaseous injector, or maybe delivered into the intake manifold as a mixture with air or acombination of air and recirculated exhaust gases, and therefore backinto the combustion chamber. In these embodiments, to help providebetter control of combustion by determining the amount of fuel beingdelivered to the combustion chamber, an air/fuel ratio measurement couldbe made using a device, such as an universal exhaust gas oxygen sensor(shown, for example at 1460 in FIG. 14) or another suitable device todetermine the fuel content of the gases being supplied to the injectoror the intake manifold. The signal from this device may be used in afeedback control loop configuration and would modify the flow of eitherthe gaseous fuel or the amount of air metered into the mixture enteringthe combustion chamber, as is conventional in the control of internalcombustion engines.

In any of the embodiments described above, it may be desired to controlthe operation of the separator, for example, to adjust a quantity offuel being separated in response to engine operating conditions. Forexample, in some situations, it may be desirable to reduce an amount ofalcohol that is extracted from a hydrocarbon fuel. Where the selectivebarrier is configured to selectively transport an alcohol, the transportof alcohol may be slowed, for example, by reducing a temperature of theseparator, by decreasing a flow of extraction fluid through theseparator, by decreasing the pressure of the mixed fuel in theseparator, or in any other suitable manner. Likewise, the transport rateof alcohol across the barrier may be increased, for example, byincreasing a temperature of the separator, by increasing a flow ofextraction fluid through the separator, by increasing a pressure of themixed fuel in the separator, or in any other suitable manner. Likewise,where the selective barrier is configured to selectively transport ahydrocarbon, the rate of hydrocarbon transport may be adjusted in likemanners. Furthermore, a bypass line (not shown) that bypasses theseparator may be provided for use in situations in which it is desirednot to separate the mixed fuel. Furthermore, separation may also becontrolled by providing a mechanism for selectively opening or closingthe second passageway of any of the embodiments of FIGS. 6-14 (where theextracted component is removed from the separators). Where thepassageway is closed from the conduits to which it is connected, thevapor pressure and/or concentration of the extracted fuel component mayincrease, which may slow and eventually stop the transport of theextracted fuel component across the barrier. It will be appreciated thatthe performance of the separators may be adjusted in response to anysuitable event or condition, including but not limited to, changingengine load, emissions conditions, different rates of consumption of thedifferent fuel fractions, etc.

In some embodiments, the performance of a separator may be monitored toprovide a greater degree of control over the separator. The performanceof the separator may be monitored in any suitable manner. For example, aseparation rate may be inferred or calculated from variables such as thetemperature of the separator, the flow rate of the mixed fuel into theseparator, the pressure of the mixed fuel within the separator, thecomposition of the mixed fuel, and/or the pressure and/or flow rate ofrecirculated exhaust gases (or other extraction fluid) within theseparator. Furthermore, the separation rate also may be calculated bymeasuring the caloric content (for example, via a UEGO sensor) of theextracted fluid, and/or by optically measuring an alcohol content of aliquid-phase extraction fluid, where the extracted fluid is an alcohol.It will be appreciated that these are merely exemplary methods ofmonitoring, calculating or estimating a performance of a separator, andthat any suitable method may be used.

The subject matter of the present disclosure includes all novel andnonobvious combinations and subcombinations of the various systems andconfigurations, and other features, functions, and/or propertiesdisclosed herein. The following claims particularly point out certaincombinations and subcombinations regarded as novel and nonobvious. Theseclaims may refer to “an” element or “a first” element or the equivalentthereof. Such claims should be understood to include incorporation ofone or more such elements, neither requiring nor excluding two or moresuch elements. Other combinations and subcombinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

1. A method of operating a vehicle system including an internalcombustion engine, comprising: separating a second fuel from a firstfuel, the second fuel having a greater concentration of at least onecomponent than the first fuel; combusting at least said first fuel atleast during a first engine load; and combusting at least said secondfuel at least during a second engine load higher than the first engineload.
 2. The method of claim 1 further comprising, increasing an amountof the second fuel that is combusted relative to an amount of the firstfuel that is combusted with increasing load.
 3. The method of claim 1further comprising, injecting the second fuel directly into at least onecylinder of the engine via a direct injector.
 4. The method of claim 3further comprising, injecting the first fuel into an intake passageupstream of an intake valve of the engine via a port injector.
 5. Themethod of claim 3 further comprising, injecting the first fuel directlyinto said at least one cylinder of the engine via the direct injector.6. The method of claim 1, wherein the component includes an alcohol. 7.The method of claim 6, wherein the alcohol includes ethanol.
 8. Themethod of claim 1, wherein the component includes water.
 9. The methodof claim 1, wherein said separating is performed at a separator.
 10. Themethod of claim 9 further comprising, applying a pressure at theseparator to at least partially separate the second fuel from the firstfuel.
 11. The method of claim 9 further comprising, adjusting acondition of the separator responsive to an operating condition, whereinthe operating condition includes at least one of a temperature of theseparator and a rate of consumption of the second fuel by the engine.12. The method of claim 9, wherein said separating includes contactingthe first fuel and the second fuel to a selective barrier of theseparator, wherein the selective barrier transports said second fuel.13. The method of claim 9 further comprising, receiving a fuel mixtureincluding the first fuel and the second fuel at a fuel tank, wherein thefuel tank is fluidically coupled to the separator; and wherein at leasta portion of the first fuel or a portion of the second fuel is returnedto the fuel tank after the second fuel is separated from the first fuel.14. The method of claim 1, wherein the second fuel is an oxygenated fuelcomponent-enriched fuel fraction and the first fuel is ahydrocarbon-enriched fuel fraction.
 15. A vehicle system, comprising: aninternal combustion engine including at least one cylinder; a separatorfor separating a second fuel and a first fuel from a fuel mixture, thesecond fuel having a greater concentration of alcohol than the firstfuel; a direct injector for injecting the second fuel directly into thecylinder; a boosting device coupled to an air passage communicating withthe engine; and a control system for: combusting at least said firstfuel in the cylinder at least during a first engine load; and combustingat least said second fuel in the cylinder at least during a secondengine load higher than the first engine load.
 16. The vehicle system ofclaim 15, wherein the alcohol includes ethanol.
 17. The vehicle systemof claim 15, further comprising a port injector for injecting the firstfuel into the air passage upstream of the engine.
 18. The vehicle systemof claim 15, wherein the control system is further configured to vary anamount of the second fuel that is combusted by the engine relative to anamount of the first fuel that is combusted by the engine responsive to alevel of boost provided to the engine by the boosting device.
 19. Thevehicle system of claim 15 further comprising, a fuel pump for applyinga pressure at the separator to at least partially separate the secondfuel from the first fuel; and wherein the control system is furtherconfigured to vary the pressure applied at the separator by the fuelpump responsive to a rate of consumption of the second fuel by theengine.
 20. (canceled)
 21. (canceled)
 22. (canceled)
 23. A method ofoperating a vehicle system including an internal combustion engine,comprising: separating a first fuel fraction from a fuel mixtureincluding said first fuel fraction and a second fuel fraction bytransporting said first fuel fraction through a selective barrier of aseparator, said first fuel fraction having a greater concentration ofethanol than said fuel mixture and said second fuel fraction; increasinga relative amount of said first fuel fraction delivered to the enginerelative to an amount of the second fuel fraction with an increasingengine load.
 24. The method of claim 23, wherein the first fuel fractionis delivered to at least one cylinder of the engine via a directinjector and at least the second fuel fraction is delivered to theengine via a second injector.
 25. The method of claim 23, wherein theengine includes a boosting device, and wherein the method furthercomprises increasing the amount of the first fuel fraction delivered tothe engine relative to the amount of the second fuel fraction with anincreasing level of boost provided to the engine by the boosting device;and wherein the second fuel fraction includes a greater concentration ofgasoline than said first fuel fraction.
 26. A method of operating avehicle system including an internal combustion engine, comprising:separating a second fuel from a first fuel, the second fuel having alower heat of vaporization than the first fuel; combusting at least saidfirst fuel at least during a first engine load; and combusting at leastsaid second fuel at least during a second engine load higher than thefirst engine load.